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Periods/Phases of Hematopoiesis

Adult Hematopoietic Tissue

Stem cell Theories and

Cell Production

Prof. Marilyn Uy-Garzon, RMT, MAST

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Mesoblastic Period 

Hepatic Period 

Myeloid/Medullary Period 

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Mesoblastic Period 

19 ± 20 days of gestation (2nd

week)

blood islands of the yolk sac

Primitive erythroblasts

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Mesoblastic Period 

Portland

Gower I

Gower II

2 2

2

2

2 2

Hematopoeitic Dev¶tal. Periods ±

cont.

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Hepatic Period 

definitive morphologic hematopoiesis

Hematopoeitic Dev¶tal. Periods ±

cont.

5th and 6th week of gestation

fetal hgb = 2 alpha and 2 gamma

fetal liver: primary erythroid organ

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Hematopoeitic Dev¶tal. Periods ±

cont.

Hepatic Period 

spleen thymus lymph nodesFetal hepatic

hematopoiesis

 Adult

extramedullary

hematopoiesis

rare

BM failure

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Myeloid/Medullary Period 

5th month of gestation

bone marrow (long bones)

Hb A1

4th year of life = marrow replaced by fats

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Bone Marrow Lymph Nodes

Spleen Liver

Thymus

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Bone Marrow 

Tissue within cavities of cortical bones

2 Types:

RED MARROW YELLOW MARROW

Hematopoietically active

Flat bones & proximal ends of long bones

Hematopoietically inactive

Adipocytes

50% red marrow, 50% yellow marrow

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Liver

Hematopoietic functions (adults):

Transport CHON synthesis

Storage of Minerals and Vitamins

Bilirubin Conjugation

Bilirubin transportation

Major site in hepatic hematopoiesis (fetus)

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Liver

Pathophysiology:

porphyriasEnzymatic deficiencies

 Accumulation of intermediary

porphyrins

Bilirubin

conjugationFe++ storage

Severe H.A. & RBC dysplasias

Extramedullary

hematopoiesisBone marrow failure

Storage diseases Monocytes/macrophages (Kupffer 

cells)

Enzymatic deficiencies

Hepatomegaly with liver 

dysfunction

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Spleen Largest lymphoid organ

Vital but not essential for life

Functions:

Indiscriminate filter of blood

sequesters senescent red cells

CULLING

PITTINGStorage for platelets (1/3)

IgM synthesis

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Spleen

Pathophysiology:

hemolysis Increased environmental stress

splenomegaly

hypersplenism

Enlarged

Enlarged

Palpable

Pancytopenia

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Lymph Nodes Members of lymphatic system

Functions:

Formation of new lymphocytes

Processing of specific Igs

Filter particulate matter, debris, bacteria

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Lymph Nodes

Pathophysiology:

adenitis

Infiltration by malignant cells

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Thymus Efficient, well-developed at birthAtrophies with age

Pathophysiology:

Non-devt (gestation) Lack of T-lymphocytes

Uncontrollable infections

DeathThymic disturbance

(adults)No effect

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PLURIPOTENTIAL STEM CELL 

One cell gives rise the varied blood

cells (E, L, M)  

COMMITTED STEM CELLS

Give rise to descendants or progeny

cells that eventually becomerestricted to a specific cell line

development

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THSC

CFU-S

CFU-L

CFU-B

CFU-T

CFU-EBFU-E

CFU-Meg

CFU-Eo

CFU-GM

T - lymphocytes

B - lymphocytes

Neutrophils

Monocytes

Eosinophils

Basophils

Platelets

Erythrocytes

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F actors That Stimulate Hematopoiesis

ERYTHROPO

IESIS

LEUKOPOIE

SISMEGAKARYOCYT

OPOIESIS

Erythropoietin

HypoxiaColony stimulatingfactors

Interleukins

Thrombopoietin

Meg-CSF

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SUMMARY

Periods/Phases of Hematopoiesis

Adult Hematopoietic Tissue

Stem cell Theories and

Cell Production